OTTAWA - A Senate probe into a leaked audit quickly became a forum for senators to air grievances against the auditor general on Tuesday.

The Senate rules committee is examining who leaked major components of Auditor General Michael Ferguson's forensic audit of spending by 106 current and former senators. Ferguson appeared at the committee Tuesday morning to discuss his office's security measures and discuss the leak.

Instead, senators' questions mainly took aim at an interview Ferguson gave ahead of the report's release. Presented with an incorrect number, Ferguson said in the interview that auditors found issues with the expenses of 30 senators. 

Ferguson said he was presented with a higher number - that 40 to 50 senators were implicated - and wanted to correct that information. He said he had been concerned that, once the report was released, a discrepancy in the numbers could raise questions among journalists.

The auditor general's office hired a security consultant to investigate the leak, and based on that report Ferguson said he's confident the disclosure didn't come from his office.

But he also revealed the office has lost a USB key containing information related to the Senate audit. A spokesman for Ferguson wasn't immediately able to answer questions about the misplaced flash drive, including who lost it.

The May 26, 2015 interview seemed to irritate senators who signed confidentiality agreements and refused to answer questions from reporters.

"You clearly indicated that you didn't have an identified or a credible source of the 40 or 50 [number]," Conservative Senator Kelvin Ogilvie said. "You were under no more pressure than any of us as individuals, senators, who were in front of cameras... there was no more need for you to give any credibility to any number than there was for any of us to respond with regard to our own personal situation."

Ferguson said he made the decision on the spur of the moment after going in to do an interview on a separate matter. "I felt that it was the right decision to make, and I still feel it was the right decision to make," he said.

The auditor general said a number of people had access to the information about the total number of senators implicated, including members of the Senate audit subcommittee working on the issue, as well as then-Senate Speaker Leo Housakos and both the Conservative and independent Liberal leaders at the time, Claude Carignan and James Cowan. Twelve copies of the report went to the Senate and 11 to auditor general staff. Ferguson said none were provided to the Prime Minister's Office.

A Huffington Post report last December cited two unnamed sources blaming Housakos for the leak. On Twitter, Housakos referred to it as a smear job.

In a statement, Housakos's spokeswoman said the story was simply "salacious rumours and innuendo."

"The work being done to reform the Senate is too important... We will not be deterred from our commitment to be more efficient, transparent and accountable,” Jacqui Delaney said.